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SubjectRe: [PATCH] hugetlb_cgroup: fix imbalanced css_get and css_put pair for shared mappings
Hi Miaohe,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on next-20210125]
[also build test ERROR on v5.11-rc7]
[cannot apply to linux/master linus/master hnaz-linux-mm/master v5.11-rc7 v5.11-rc6 v5.11-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Miaohe-Lin/hugetlb_cgroup-fix-imbalanced-css_get-and-css_put-pair-for-shared-mappings/20210210-171736
base: 59fa6a163ffabc1bf25c5e0e33899e268a96d3cc
config: x86_64-randconfig-c002-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/68f4ed1b80aa7c51a921c3ad913ee7e6e00618d0
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Miaohe-Lin/hugetlb_cgroup-fix-imbalanced-css_get-and-css_put-pair-for-shared-mappings/20210210-171736
git checkout 68f4ed1b80aa7c51a921c3ad913ee7e6e00618d0
# save the attached .config to linux build tree
make W=1 ARCH=x86_64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

mm/hugetlb.c: In function 'hugetlb_reserve_pages':
>> mm/hugetlb.c:5222:17: error: dereferencing pointer to incomplete type 'struct hugetlb_cgroup'
5222 | css_put(&h_cg->css);
| ^~


vim +5222 mm/hugetlb.c

5091
5092 /* Return true if reservation was successful, false otherwise. */
5093 bool hugetlb_reserve_pages(struct inode *inode,
5094 long from, long to,
5095 struct vm_area_struct *vma,
5096 vm_flags_t vm_flags)
5097 {
5098 long chg, add = -1;
5099 struct hstate *h = hstate_inode(inode);
5100 struct hugepage_subpool *spool = subpool_inode(inode);
5101 struct resv_map *resv_map;
5102 struct hugetlb_cgroup *h_cg = NULL;
5103 long gbl_reserve, regions_needed = 0;
5104
5105 /* This should never happen */
5106 if (from > to) {
5107 VM_WARN(1, "%s called with a negative range\n", __func__);
5108 return false;
5109 }
5110
5111 /*
5112 * Only apply hugepage reservation if asked. At fault time, an
5113 * attempt will be made for VM_NORESERVE to allocate a page
5114 * without using reserves
5115 */
5116 if (vm_flags & VM_NORESERVE)
5117 return true;
5118
5119 /*
5120 * Shared mappings base their reservation on the number of pages that
5121 * are already allocated on behalf of the file. Private mappings need
5122 * to reserve the full area even if read-only as mprotect() may be
5123 * called to make the mapping read-write. Assume !vma is a shm mapping
5124 */
5125 if (!vma || vma->vm_flags & VM_MAYSHARE) {
5126 /*
5127 * resv_map can not be NULL as hugetlb_reserve_pages is only
5128 * called for inodes for which resv_maps were created (see
5129 * hugetlbfs_get_inode).
5130 */
5131 resv_map = inode_resv_map(inode);
5132
5133 chg = region_chg(resv_map, from, to, &regions_needed);
5134
5135 } else {
5136 /* Private mapping. */
5137 resv_map = resv_map_alloc();
5138 if (!resv_map)
5139 return false;
5140
5141 chg = to - from;
5142
5143 set_vma_resv_map(vma, resv_map);
5144 set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
5145 }
5146
5147 if (chg < 0)
5148 goto out_err;
5149
5150 if (hugetlb_cgroup_charge_cgroup_rsvd(hstate_index(h),
5151 chg * pages_per_huge_page(h), &h_cg) < 0)
5152 goto out_err;
5153
5154 if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
5155 /* For private mappings, the hugetlb_cgroup uncharge info hangs
5156 * of the resv_map.
5157 */
5158 resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);
5159 }
5160
5161 /*
5162 * There must be enough pages in the subpool for the mapping. If
5163 * the subpool has a minimum size, there may be some global
5164 * reservations already in place (gbl_reserve).
5165 */
5166 gbl_reserve = hugepage_subpool_get_pages(spool, chg);
5167 if (gbl_reserve < 0)
5168 goto out_uncharge_cgroup;
5169
5170 /*
5171 * Check enough hugepages are available for the reservation.
5172 * Hand the pages back to the subpool if there are not
5173 */
5174 if (hugetlb_acct_memory(h, gbl_reserve) < 0)
5175 goto out_put_pages;
5176
5177 /*
5178 * Account for the reservations made. Shared mappings record regions
5179 * that have reservations as they are shared by multiple VMAs.
5180 * When the last VMA disappears, the region map says how much
5181 * the reservation was and the page cache tells how much of
5182 * the reservation was consumed. Private mappings are per-VMA and
5183 * only the consumed reservations are tracked. When the VMA
5184 * disappears, the original reservation is the VMA size and the
5185 * consumed reservations are stored in the map. Hence, nothing
5186 * else has to be done for private mappings here
5187 */
5188 if (!vma || vma->vm_flags & VM_MAYSHARE) {
5189 add = region_add(resv_map, from, to, regions_needed, h, h_cg);
5190
5191 if (unlikely(add < 0)) {
5192 hugetlb_acct_memory(h, -gbl_reserve);
5193 goto out_put_pages;
5194 } else if (unlikely(chg > add)) {
5195 /*
5196 * pages in this range were added to the reserve
5197 * map between region_chg and region_add. This
5198 * indicates a race with alloc_huge_page. Adjust
5199 * the subpool and reserve counts modified above
5200 * based on the difference.
5201 */
5202 long rsv_adjust;
5203
5204 /*
5205 * hugetlb_cgroup_uncharge_cgroup_rsvd() will put the
5206 * reference to h_cg->css. See comment below for detail.
5207 */
5208 hugetlb_cgroup_uncharge_cgroup_rsvd(
5209 hstate_index(h),
5210 (chg - add) * pages_per_huge_page(h), h_cg);
5211
5212 rsv_adjust = hugepage_subpool_put_pages(spool,
5213 chg - add);
5214 hugetlb_acct_memory(h, -rsv_adjust);
5215 } else if (h_cg) {
5216 /*
5217 * The file_regions will hold their own reference to
5218 * h_cg->css. So we should release the reference held
5219 * via hugetlb_cgroup_charge_cgroup_rsvd() when we are
5220 * done.
5221 */
> 5222 css_put(&h_cg->css);
5223 }
5224 }
5225 return true;
5226
5227 out_put_pages:
5228 /* put back original number of pages, chg */
5229 (void)hugepage_subpool_put_pages(spool, chg);
5230 out_uncharge_cgroup:
5231 hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
5232 chg * pages_per_huge_page(h), h_cg);
5233 out_err:
5234 if (!vma || vma->vm_flags & VM_MAYSHARE)
5235 /* Only call region_abort if the region_chg succeeded but the
5236 * region_add failed or didn't run.
5237 */
5238 if (chg >= 0 && add < 0)
5239 region_abort(resv_map, from, to, regions_needed);
5240 if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
5241 kref_put(&resv_map->refs, resv_map_release);
5242 return false;
5243 }
5244

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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